Abstract: An apparatus for supplying high purity gas comprises a cylinder having a valve with two internal ports. One internal port is used to fill the cylinder while the other is fitted with a unit which removes particulates and impurities from the gas as it leaves the cylinder. The unit comprises an inlet, a first filter for removing coarse particulates, layers of adsorbent and absorbent for removing impurities, and a second filter for removing fine particulates. The purified gas leaves the cylinder via the valve and after passing through a regulator, a flow control device and various lengths of tubing passes through a conventional purifier immediately upstream of the point of use. The apparatus reduces the load on the purifier and hence decreases the frequency at which the purifier has to be recharged. Potentially the apparatus could obviate the need for the purifier altogether.